(a) Field
The present invention relates to a machine tool provided with a headstock movable in the axial direction of a main spindle.
(b) Description of the Related Art
A sliding headstock type lathe is conventionally known in which a workpiece is slidably supported by a guide bush mounted on the front side of the main spindle. A headstock provided with the main spindle is movalble in the axial direction of the main spindle by a driving unit including a ball screw (feed mechanism) mounted in the axial direction, a nut mounted on the headstock to be engaged with the ball screw, and a servo motor for rotatably driving the ball screw. The headstock is provided with a ball screw cover for safety or for protection, for example, from workpiece dust.
In a sliding headstock type lathe disclosed in Japanese Patent Application Publication No. H9-225703, a guide bush holder is detachably mounted on a supporting bed. When the guide bush is not used, the guide bush holder is replaced by a cover having a protective hole into which the leading end of the main spindle is to be inserted. The replacement cover is not a cover for the ball screw.